1. Field of the Invention
The present invention relates to an electrostatic sprayer for electrifying a sprayed agricultural chemical or any other chemical and scattering the chemical over a cultivated plant or the like.
2. Description of the Related Art
Electrostatic sprayers having electrostatic electrodes located in front of the outlets of spray nozzles have been put to use in the past. The electrostatic electrodes are used to electrify sprays jetted from the spray nozzles. Using the electrostatic sprayer, since sprays jetted from the spray nozzles are electrified, the sprays highly efficiently adhere to a field crop or the like whose polarity is opposite to that of the sprayed particles of a chemical. This leads to improved certainty of control.
The electrostatic sprayer has an electrostatic circuit like the one shown in FIG. 3 or FIG. 4 included in a sprayer body. In the electrostatic circuit shown in FIG. 3, a transistor 3 connected to a battery 1 is driven with a pulse output from a trigger circuit 2 that is driven using the battery 1 as a power supply. A pulsating voltage output from the transistor 3 is stepped up using a step-up transformer 4. Consequently, a high voltage is applied to an electrostatic electrode 6 via a rectifier diode 5. Incidentally, a triggering voltage output circuit or an oscillatory circuit is adopted as the trigger circuit 2. The triggering voltage output circuit 2 outputs a triggering voltage which a trigger coil induces synchronously with rotation of an internal combustion engine.
Furthermore, in the electrostatic circuit shown in FIG. 4, a voltage developed by a battery 1 is converted into a direct voltage of a predetermined level by means of a DCxe2x80x94DC converter 7. The direct voltage is applied to a charge/discharge capacitor 9 via a reverse-current prevention diode 8 and a primary winding 4a of a step-up transformer 4, whereby the charge/discharge capacitor 9 is charged. Meanwhile, a thyristor 10 becomes conducting with a pulse output from a trigger circuit 2 that is driven using the battery 1 as a power supply. Charge in the charge/discharge capacitor 9 is supplied to the primary winding 4a of the step-up transformer 4 via the thyristor 10. A high-voltage pulse induced in the secondary winding 4b is applied to an electrostatic electrode 6 via a rectifier diode 5.
In general, the electrostatic sprayer has a nozzle boom 11, to which a plurality of spray nozzles 12 is coupled, incorporated together with a chemical tank and the battery 1 on a movable sprayer body. A high-voltage 20 cable to which the step-up transformer 4 and rectifier diode 5 are coupled is extended along the nozzle boom 11, whereby a high direct voltage is applied to each electrostatic electrode 6 located in front of each of the spray nozzles 12.
However, in the conventional electrostatic sprayer, the high-voltage cable 20 is extended from the step-up transformer 4 located on a high-voltage pulse generation stage to the vicinity of each spray nozzle 12. The high-voltage cable 20 is so long that a high voltage stepped up by the step-up transformer 4 largely drops by the time that the high voltage reaches each electrostatic electrode 6 because of a resistance loss caused by the so long high-voltage cable 20. The number of electrostatic electrodes 6 capable of being connected to one step-up transformer 4 is therefore limited. Moreover, a voltage leakage may occur along the way of the high-voltage cable 20. Efficiency in electrifying a spray may deteriorate due to a drop of a voltage to be applied to the electrostatic electrode 6.
An object of the present invention is to provide an electrostatic sprayer capable of highly efficiently applying a high voltage produced by a step-up transformer to an electrostatic electrode with a loss minimized.
For accomplishing the above object, in an electrostatic sprayer in accordance with the present invention, a pulsating voltage developed using a battery or a generator as a power supply is stepped up using a step-up transformer. The resultant high-voltage pulse is rectified and applied to an electrostatic electrode located near a spray nozzle. Thus, a spray jetted from the spray nozzle is electrified. The step-up transformer is located near the spray nozzle.
According to the present invention, the length of a high-voltage cable from the step-up transformer to the electrostatic electrode is so short as to minimize the adverse effect of a resistance caused by the excessively long high-voltage cable. Consequently, the resultant high voltage is highly efficiently applied to the electrostatic electrode.
In a preferred embodiment of the present invention, at least part of the spray nozzle may be used as a core of the step-up transformer. In this case, the step-up transformer itself and the electrostatic electrode can be confined to the smallest possible sizes.